An over-simplification:
MCAT = applying general knowledge to questions. You get good at CARS, for example, by doing CARS problems, and you solve novel physics questions by applying physicals formulas you already know. The main source of memorization is probably biology. The "meat" of the test comes from several classes, and you can study for several months.
Step 1 = mostly memorization. You get presented with information about a patient and have to make a diagnosis, or pick a treatment, that fits profiles you have memorized. For example, the patient has symptoms X, Y, and Z, which fits diagnosis 1 the best, which is best treated with treatment A. For stuff you don't know, it's a combination of applied knowledge and answer elimination. Everything covered in your first two years of classes (and more) is fair game, and you generally have a few weeks to study.